Timing Chain?

Hi there, i was wondering if anyone knows how much it costs to fix a timing chain on a Vauxhall Corsa 1.2 sxi model? 52 plate. I have been quoted over £500 from vauxhall which includes parts and oil filter change as well as labour, too expensive i thought, anyone else have the same problem as me? Ive been told that Vauxhall say the timing chain should last the life of the car, but yet its gone? what to do? any help would be much obliged :-). Thank you people.

thanks again